JPWO2008114583A1 - In-vehicle communication system - Google Patents

Abstract

In an in-vehicle communication system in which a plurality of buses are relay-connected through relay connection units and at least one ECU is connected to each bus, a basic routing table that specifies relay destinations to be transmitted from the relay connection unit to the ECU is stored in the ROM. A transmission list report message related to the ID of the message is transmitted, and from the ECU that has received the transmission list report message, a transmission request message related to the ID of the message to be received that is not included in the transmission list report message is sent to the relay connection unit. A new additional routing table indicating the correspondence between the ID requested by the transmission request message and the transmission destination is created by the table creation unit of the relay connection unit that has received the transmission request message in response and stored in the RAM. ing.

Description

  The present invention relates to an in-vehicle communication system, and in particular, manages a message transmission destination by a relay connection unit that relay-connects a plurality of buses, and creates a new program even when a relay message is added. This eliminates the need for incorporation into the relay connection unit and enables automatic processing within the relay connection unit.

  Conventionally, a communication line (hereinafter referred to as a bus) connected to an electronic control unit (ECU) for controlling equipment mounted on an automobile is relay-connected by a relay connection unit such as a gateway, and between each ECU. An in-vehicle communication system that transmits and receives messages is employed.

  In recent years, with the increase in functions of automobiles, the number of ECUs has increased, and the number of messages transmitted and received between ECUs has also increased rapidly. Therefore, in order to relay messages between ECUs, a relay connection unit (so-called gateway) is interposed between the buses connected to the ECUs to improve the efficiency of message transmission / reception between ECUs and reduce the communication load factor of the buses. is doing.

  For example, in Japanese Patent Laid-Open No. 2003-264571 (Patent Document 1), a routing table of a list storing a correspondence relationship between a message ID (identifier) to be relayed to a relay connection unit and a destination bus is provided in the ROM. The communication load factor is reduced by referring to the routing table and relaying the message to the destination bus and not transmitting the message to other buses.

JP2002-176430

However, the ROM for storing the routing table is incorporated as a program when the relay connection unit is manufactured, and the message ID and the destination bus are specified in advance. Therefore, when a new ECU is connected to a bus that is not a transmission destination or an ECU function is added, and the ECU wants to receive a message, a routing table stored in the ROM that cannot be rewritten. Information cannot be received from the relay connection unit. That is, there is a problem that the communication system cannot be added or changed or shared with other vehicle types.
To solve the problem, it is possible to replace the ROM of a new program with added transmission / reception support and incorporate it into the relay connection unit. It is not preferable to replace it.

  On the other hand, in a general communication system that is not a communication system for automobiles, there are many different types of communication devices. Therefore, the message IDs required by each communication apparatus are often different from one another. Therefore, information to be transmitted / received via the relay connection unit tends to be more information added later than information stored in the ROM. Therefore, there is a problem that many messages are intensively transmitted / received via the communication line in setting ID information at the time of starting the apparatus equipped with the communication device, the communication load factor becomes high, and it takes time to create the table. .

  The present invention has been made in view of the above problems, and is a basic routing table stored in a ROM incorporated in a relay connection unit at the time of manufacture, and a request to be received from the ECU side regarding a bus that has not been a transmission destination. If there is, there is no need to replace it with a new ROM that stores the additional routing table, and the relay connection unit can automatically add the routing table so that the communication system can be changed and shared with other models. An object is to provide an in-vehicle communication system that can be used.

In order to solve the above problems, the present invention provides an in-vehicle communication system in which a plurality of buses are connected via a relay connection unit, and at least one electronic control unit is connected to each bus.
The relay connection unit is
A ROM storing a basic routing table indicating a correspondence between a message ID (identifier) to be relayed and a destination bus, and a RAM storing a rewritten additional routing table indicating a newly added correspondence A storage unit having
A message creation unit for creating a transmission list report message indicating a correspondence relationship between a message ID (identifier) and a destination bus to be relayed based on the basic and additional routing table of the storage unit;
A table creation unit for creating an additional routing table stored in the RAM;
With
The relay connection unit transmits the transmission list report message to all connected buses,
The electronic control unit that has received the transmission list report message via the bus transmits a transmission request message of a message ID that has not been received among necessary message IDs to the relay connection unit,
The relay connection unit that has received the transmission request message is an addition indicating the correspondence between the message ID requested in the transmission request message and the destination bus to which the requested electronic control unit is connected in the table creation unit. A new in-vehicle communication system is provided in which a new routing table is created for each minute and the RAM is rewritten and stored.

The in-vehicle communication system is constructed on the basis of the characteristics of communication equipment mounted on an automobile.
In a general communication system other than an automobile, a wide variety of communication devices are connected via a relay connection unit. In an automobile, a communication device connected to the relay connection unit is assumed as an option in advance. There are very few cases where a completely new communication device is connected.
Therefore, a bus that connects the optional communication device and the relay connection unit can be assumed, and a correspondence relationship between the message ID relayed and transmitted by the relay connection unit and the bus can be assumed in advance. Based on the characteristics of such an automobile communication system, a basic ROM routing table is created including optional communication devices. In other words, the basic routing table stored in the ROM is assumed to store in advance correspondence relationships including possible options. Therefore, it is assumed that there are very few additional routing tables newly added and stored by rewriting the RAM.
As described above, almost all message IDs required by the communication device are assumed and stored in the basic routing table of the ROM. Therefore, only a few messages are transmitted and received when setting additional message IDs at the time of startup. Concentration is avoided and can be done in a very short time.

Specifically, the bus connected to the electronic control unit and the relay connection unit includes a CAN communication line.
The message received by the relay connection unit via the bus is transmitted to the corresponding bus with reference to the routing table stored in the memory and relayed. Therefore, when a bus of another communication system that is not stored in the routing table of the storage unit is connected to the relay connection unit, when a new electronic control unit is connected to the already connected bus, the bus is already connected via the bus. When the function of the electronic control unit connected in this way is added, the message cannot be received from the relay connection unit because it is not described in the routing table.
In the in-vehicle communication system of the present invention, the transmission list report message is transmitted to all the buses connected from the relay connection unit. Therefore, the transmission list report message is also transmitted to the bus newly connected to the relay connection unit, and the electronic control unit connected to the additional bus can receive the transmission list report message.
The added electronic control unit selects a message ID to be received based on the received transmission list report message, and transmits a transmission request message to the relay connection unit via the bus.
The relay connection unit that has received the transmission request message can know the message ID that needs to be newly transmitted and the bus to which the requested electronic control unit is connected, and the correspondence between the message ID and the destination bus Can be created by the table creation unit, and the created additional routing table can be rewritten and stored in the RAM.
With reference to the additional routing table newly stored in the RAM, a message having a message ID that needs to be newly transmitted is transmitted to the corresponding bus, and the additional electronic control unit connected to the bus needs the necessary message. Can be received.

The function of the electronic control unit already connected to the bus is added when a new electronic control unit is connected to the already connected bus, not only when a new bus is connected to the relay connection unit described above. Similarly, in any case, the electronic control unit receives the transmission list report from the relay connection unit, and transmits the transmission request of the necessary message ID that has not been received to the relay connection unit. An additional routing table can be created by the table creation unit, the RAM can be rewritten, and a message ID and a transmission bus can be added.
Therefore, it is not necessary to incorporate a ROM that stores a new program that has been added or changed in the relay connection unit, and the RAM can be rewritten to cope with the addition. Therefore, versatility can be improved and it can be shared with communication systems of other vehicle types. Become.

The transmission list report message transmitted from the relay connection unit is created with reference to both the basic routing table stored in the ROM and the additional routing table already written in the RAM.
As described above, the transmission list report message sent from the relay connection unit is created by referring to both the basic routing table stored in the ROM and the additional routing table stored in the RAM. Transmission request messages can be reduced.

The transmission list report message M1 includes the ID of the message to be transmitted and the data length.
Thus, by including not only the message ID but also the data length, the electronic control unit that has received this transmission list report message can know the change of the message transmitted from the relay connection unit, and based on that Whether or not a transmission request is required can be determined.

The electronic control unit is
A storage unit for storing a reception list table indicating message IDs to be received;
A comparison unit that compares the transmission list report message with the reception list table and detects a message ID that is included in the reception list table but not included in the transmission list report message;
A message creating unit that creates the transmission request message related only to the message ID detected by the comparing unit;
The transmission request message created by the message creation unit is transmitted to the relay connection unit.

  As described above, since messages that request transmission from each electronic control unit to the relay connection unit are excluded from messages that have already been transmitted to the bus to which the electronic control unit is connected, the amount of transmission request messages is reduced, It is possible to reduce the time required for creating an additional routing table in the relay connection unit without increasing the communication load factor.

The transmission list report message and the transmission request message are transmitted and received between the relay connection unit and the electronic control unit, and the process of creating an additional routing table in the relay connection unit is performed by the relay connection unit or the electronic control of the in-vehicle communication system. Preferably, the unit is at start-up connected to a battery.
In addition, depending on the device connected to the bus, the process may be executed when the ignition key is operated to change from the off state to the accessory state or the on state.

As described above, according to the present invention, the relay connection unit includes the ROM that stores the basic routing table and the RAM that rewrites and stores the additional routing table to be added to the relay. A send list message is being sent to. If the electronic control unit connected to each bus transmits only the message ID to be transmitted based on the transmission list message to the relay connection unit, the relay connection unit creates an additional routing table in the table creation unit and stores it in the RAM. The additional message table is rewritten and stored.
Therefore, when the electronic control unit of the bus newly connected to the relay connection unit, when the electronic control unit is newly added to the already connected bus, or when the function of the electronic control unit already connected to the bus is added The message that the electronic control unit wants to receive can be automatically transmitted to any electronic control unit. As described above, even if relays are added, it is not necessary to use a ROM having a new basic routing table, and it can be handled by a RAM, and the sharing of an electronic control unit can be promoted.

In particular, in the in-vehicle communication system of the present invention, an optional additional communication device can be assumed in advance, and a message required by the electronic control unit of the communication device that can be assumed and a bus to be connected can be assumed. The relationship with the bus can be stored in advance in the basic routing table of the ROM.
That is, the message ID transmitted to and received from the electronic control unit of the optional device that is not yet connected to the relay connection unit via the bus in the basic routing table of the relay connection unit ROM; The correspondence relationship with the bus is stored in advance, so that an additional routing table to be written into the RAM is reduced. As a result, the number of message IDs for which a transmission request is issued from the electronic control unit side based on a transmission list message report transmitted from the relay connection unit to all buses at the time of startup of the automobile can be made small. Concentration of communication can be avoided, and communication processing of transmission requests can be completed in a short time.

It is drawing which shows 1st Embodiment of this invention and shows the operation | movement at the time of startup after a vehicle-mounted communication system design change. It is drawing before the design change of a vehicle-mounted communication system. It is a block diagram of a relay connection unit. It is a block diagram of ECU. (A) is a diagram schematically showing a message format, (B) and (C) are transmission list report messages, and (D) and (E) are diagrams showing transmission request messages. It is a flowchart which shows the operation | movement after starting a vehicle-mounted communication system. It is drawing which shows 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 In-vehicle communication system 11 Communication line 20 Relay connection unit 22 CPU
23 ROM (storage unit)
24 RAM
25 relay processing unit 26 message creating unit 27 table creating unit 30 ECU (electronic control unit)
32 CPU
33 ROM
34 Comparison unit 35 Message creation unit JT Reception list table M Message M1 (M1-1, M1-2) Transmission list report message M2 (M2-1, M2-2) Transmission request message T Basic routing table NT New routing table

Embodiments of the present invention will be described with reference to the drawings.
1 to 6 show a first embodiment of the present invention.
An in-vehicle communication system 10 (hereinafter referred to as a communication system 10) according to the present embodiment includes communication lines (buses) 11A and 11B whose communication protocol is CAN are connected via a relay connection unit (gateway) 20, and a communication network. Is configured. A plurality of ECUs 30 (electronic control units) are connected to the communication lines 11A and 11B, respectively.

As shown in FIG. 3, the relay connection unit 20 is connected to communication lines 11A and 11B via transmission / reception units 21A and 21B. The transmission / reception units 21A and 21B are connected to the CPU 22, and the CPU is a storage unit. Are connected to a ROM 23 and a RAM 24.
The CPU 22 reads the basic routing table T stored in the read-only and non-rewritable ROM 23 and the additional routing table NT stored in the rewritable RAM (hereinafter the basic routing table T and the additional routing table NT together) Connected).
The CPU 22 refers to the routing table, determines the necessity of relaying the message M and the relay destination communication line, and creates a transmission list report message M1 by referring to the routing table. 26 and a table creation unit 27 that creates a new additional routing table NT based on a transmission request message M2 (described later) received from the ECU 30.

As described above, the ROM 23 of the storage unit stores the basic routing table T created by the program incorporated when the relay connection unit 20 is manufactured.
The basic routing table T stored in the ROM 23 is not yet connected to the relay connection unit 20 via a bus, but is set as an optional communication device and connected to the relay connection unit 20 or to be connected. The correspondence between the message ID required by the electronic control unit of the optional communication device connected to the bus and the bus is also stored in the basic routing table T in advance. Thereby, the newly added routing table can be reduced in advance.
On the other hand, in the RAM 24, the newly added additional routing table NT created by the table creating unit 27 is rewritten and stored.

On the other hand, as shown in FIG. 4, the ECU 30 connected to all communication lines (buses) connected to the relay connection unit 20 is connected to the transmission / reception unit 31 connected to the communication line 11A (11B), and the necessary processing. CPU 32 which performs and storage part 33 are provided.
The CPU 32 compares the transmission list report message M1 transmitted from the relay connection unit 20 with the reception list table JT stored in the storage unit 33, and transmits based on the detection result by the comparison unit 34. A message creation unit 35 for creating the request message M2 is provided. The ECU 30 is connected to devices to be controlled, switches, sensors, etc., but is not shown.

Specifically, the ROM 23 of the storage unit of the relay connection unit 20 stores the ID (identifier) of the message M transmitted and received in the communication system 10 and the transmission destination (CAN1 on the communication line 11A side or CAN2 on the communication line 11B side). A basic routing table T indicating the correspondence is stored.
As shown schematically in FIG. 5A, the message M includes an ID and a data part. When the transmission / reception parts 21 </ b> A and 21 </ b> B of the relay connection unit 20 receive the message M, the relay processing part 25 of the CPU 22 performs the basic operation of the ROM 23. With reference to the routing table T, the message M is relayed to the designated destination communication line 11A or 11B, or is not relayed if relaying is not required. When relaying, it transmits to communication line 11A, 11B via transmission / reception part 21A, 21B. For example, a message whose ID is “0x600” is transmitted to the communication line 11A, and a message M whose ID is “0x700” is transmitted to the communication line 11B.
In addition, when the additional routing table NT that has been added and rewritten, which will be described later, is stored in the RAM 24, the relay processing unit 25 refers to both the basic routing table T in the ROM 23 and the additional routing table NT stored in the RAM 24. And relay.

When there is a basic routing table T stored in the ROM 23 and an additional routing table NT stored in the RAM, the message creating unit 26 of the CPU 22 refers to the additional routing table and refers to FIG. A transmission list report message M1 shown in (C) is created (step S1 in FIG. 6).
The transmission list report message M1 describes the ID of the message to be transmitted in the data part, and the ECU 30 that has received the transmission list report message M1 transmits what message M is transmitted from the relay connection unit 20. Can know.

Next, a procedure for creating a new additional routing table NT in the relay connection unit 20 will be described with reference to FIG.
As described above, the basic routing table T of the ROM 23 stores in advance the correspondence relationship between the assumed message ID and the destination communication line (bus), and reduces the additional routing table NT that is newly rewritten in the RAM. is doing.

The transmission list report message M1 is transmitted to all communication lines (in this embodiment, communication lines 11A and 11B) to which the relay connection unit 20 is connected. (Step S2 in FIG. 6)
When the transmission / reception unit 31 of the ECU 30 receives the transmission list report message M1, the comparison unit 34 of the ECU 30 receives the ID described in the data part of the transmission list report message M1 and the reception list table indicating the ID of the message to be received. The ID of JT (stored in ROM 33) is compared, and an ID that is included in the reception list table JT but not included in the transmission list report message M1 is detected. (Step S3 in FIG. 6)
Based on this detection result, the message creation unit 35 of the CPU 32 creates a transmission request message M2 shown in FIGS. 5D and 5E in which the ID of a message requesting additional transmission is described in the data part. (Step S4 in FIG. 6)

The ECU 30 transmits a transmission request message M2 to the relay connection unit 20. (Step S5 in FIG. 6)
When the transmission / reception units 21A and 21B of the relay connection unit 20 receive the transmission request message M2, the table creation unit 27 of the relay connection unit 20 associates the ID of the message newly requested for transmission with the transmission destination of the message. A new additional routing table NT specifying the relationship is created by rewriting the RAM 24. (Step S6 in FIG. 6)

  After the new additional routing table NT is created, the relay processing 25 of the relay connection unit 20 refers to both the basic routing table T stored in the ROM 23 and the new additional routing table NT stored in the RAM 24. Relay.

Next, the case where the communication system 10 is changed from the state shown in FIG. 2 to the state shown in FIG. 1 will be specifically described.
The number of control objects of the ECU 30A is increased, and the ECU 30F is newly connected to the communication line 11B.
When the relay connection unit 20 and the ECU 30 of the communication system 10 are connected to the battery and activated, the message creation unit 26 of the relay connection unit 20 refers to the basic routing table T stored in the ROM 23 and is shown in FIGS. The transmission list report messages M1-1 and M1-2 shown in FIG. 6 are created (step S1 in FIG. 6).
In the step S1, the additional routing table is not stored in the RAM.
The transmission list report message M1-1 is a message transmitted to the communication line 11A, and the ID “0x400” “0x600” of the message transmitted to the communication line 11A is included in the data part of the transmission list report message M1-1. “0x800” is described. Therefore, the ECUs 30 </ b> A to 30 </ b> C that have received the transmission list report message M <b> 1-1 can know that the message M having the ID “0x400”, “0x600”, or “0x800” is transmitted from the relay connection unit 20.
Similarly, the transmission list report message M1-2 is a message transmitted to the communication line 11B, and an ID “0x500” of the message M transmitted to the communication line 11B is included in the data part of the transmission list report message M1-2. "0x700" and "0x900" are described. Therefore, the ECUs 30D and 30E that have received the transmission list report message M1-2 can know that the message M having the ID “0x500”, “0x700”, or “0x900” is transmitted from the relay connection unit 20.
The ID “0x010” of the transmission list report messages M1-1 and M1-2 shown in FIGS. 5B and 5C is an ID indicating that the message is the transmission list report message M1. .

  The transmission list report message M1 created by the message creation unit 26 is transferred to the transmission / reception units 21A and 21B, the transmission list report message M1-1 is sent to the communication line 11A, and the transmission list report message M1-2 is sent to the communication line 11B. (Step S2 in FIG. 6).

As shown in FIG. 1, the comparison unit 34 of the ECU 30 </ b> A that newly needs to receive the message with the ID “0x410” is described in the data part of the transmission list report message M <b> 1-1 transmitted from the relay connection unit 20. The IDs “0x400”, “0x600”, and “0x800” are compared with the IDs “0x400”, “0x410”, and “0x800” described in the reception list table JT (step S3 in FIG. 6). As a result of this comparison, an ID “0x410” that is included in the reception list table JT but not included in the transmission list report message M1-1 is detected. In response to this detection result, the message creation unit 35 creates a transmission request message M2-1 (FIG. 5D) in which the ID “0x410” of the message requesting additional transmission is described in the data part (FIG. 5D). 6 step S4).
Also, the ID “0x500”, “0x700”, “0x900” and the reception list table JT described in the data portion of the transmission list report message M1-2 transmitted from the relay connection unit 20 by the comparison unit 34 of the newly connected ECU 30F. Are compared with the IDs “0x500” and “0x510” described in FIG. 6 (step S3 in FIG. 6). As a result of this comparison, an ID “0x510” that is included in the reception list table JT but not included in the transmission list report message M1-2 is detected. In response to this detection result, the message creation unit 35 creates a transmission request message M2-2 (FIG. 5E) in which the ID “0x510” of the message requesting additional transmission is described in the data part (FIG. 5E). 6 step S4).
Note that “0x100” described in the IDs of the transmission request messages M2-1 and M2-2 shown in FIGS. 5D and 5E is a transmission request message created by the ECU 30 connected to the communication lines 11A and 11B. Indicates M2.

  When the transmission request messages M2-1 and M2-2 shown in FIGS. 5D and 5E are transmitted from the ECUs 30A and 30F (step S5 in FIG. 6) and received by the relay connection unit 30, the table creation unit 27 receives the ID “ A new routing table NT indicating that the message “0x410” is transmitted to the communication line 11A and the message of ID “0x510” is transmitted to the communication line 11B is created (step S6 in FIG. 6) and stored in the RAM 24. .

  After the new additional routing table NT is created, the ID is “0x400, 0x410” by referring to both the basic routing table T stored in the ROM 23 of the relay connection unit 20 and the new routing table NT stored in the RAM 24. , 0x600, 0x800 "are transmitted to the communication line 11A, and messages with IDs" 0x500, 0x510, 0x700, 0x900 "are transmitted to the communication line 11B.

Thus, even when a new ECU 30F is connected to the communication line 11B or a function of the ECU 30A is added, a new routing table NT is automatically created, and a message is also referred to by referring to the new routing table NT. Can be relayed to a specified communication line.
Also, instead of notifying all of the necessary message IDs from each ECU 30 to the relay connection unit 20, only the message IDs for which the relay connection unit 20 does not know the relay destination are notified from the ECU 30 to the relay connection unit 20. It is possible to reduce the amount of data transmitted and received between the relay connection unit 20 and the ECU 30 necessary for creating a simple routing table NT, and to create a new additional routing table NT in a short time.

FIG. 7 shows a second embodiment of the present invention.
In the communication system 10 of this embodiment, the communication line 11A and the communication line 11B are relay-connected via the first relay connection unit 20A, while the communication line 11B and the communication line 11C are relayed via the second relay connection unit 20B. The ECUs 30A and 30B are connected to the communication lines 11A and 11C, respectively. In the present embodiment, the relay connection unit 20 also includes a message creation unit that creates the transmission request message M2.

The basic routing table T of the relay connection unit 20 and the reception list table JT of the ECU 30 are as shown in FIG. 7. When the communication system 10 is activated, the transmission list report message M1 is created by the message creation unit of the relay connection units 20A and 20B. And transmitted to the required communication line 11.
Upon receiving the transmission list report message M1, the ECU 30A creates a transmission request message M2 requesting transmission of the message with the ID “0x610” and transmits it to the first relay connection unit 20A.

In the first relay connection unit 20A that has received the transmission request message M2, a new routing table NT is created. Further, in order to notify the second relay connection unit 20B of the transmission request, the message creation unit of the first relay connection unit 20A creates a transmission request message M2 for requesting transmission of the message with the ID “0x610”. The data is transmitted to the communication line 11B to which the relay connection unit 20B is connected.
In the second relay connection unit 20B that has received the transmission request message M2 from the first relay connection unit 20A, a new routing table NT indicating that the message of ID “0x610” is transmitted to the communication line 11B is created.

According to the above-described configuration, even in the communication system 10 including a plurality of relay connection units 20, it is possible to notify all relay connection units 20 of the IDs of newly requested messages. As a result, a message newly requested to be transmitted can be transmitted to the target ECU through the plurality of relay connection units 20.
In the present embodiment, the entire communication system conforms to the CAN standard. However, the whole or a part of the communication system may conform to the FlexRay standard.
In addition, since other configurations and operational effects are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.

Claims (7)

In an in-vehicle communication system in which a plurality of buses are connected via a relay connection unit, and at least one electronic control unit is connected to each bus.
The relay connection unit is
A ROM storing a basic routing table indicating a correspondence between a message ID (identifier) to be relayed and a destination bus, and a RAM storing a rewritten additional routing table indicating a newly added correspondence A storage unit having
A message creation unit for creating a transmission list report message indicating a correspondence relationship between a message ID (identifier) and a destination bus to be relayed based on the basic routing table and the additional routing table of the storage unit;
A table creation unit for creating an additional routing table stored in the RAM;
With
The relay connection unit transmits the transmission list report message to all connected buses,
The electronic control unit received in the transmission list report message via the bus transmits a transmission request message of a message ID not received among necessary message IDs to the relay connection unit,
The relay connection unit that has received the transmission request message is an addition indicating the correspondence between the message ID requested in the transmission request message and the destination bus to which the requested electronic control unit is connected in the table creation unit. A vehicle-mounted communication system, wherein a new routing table is created for each minute and the RAM is rewritten and stored. The electronic control unit is
A storage unit for storing a reception list table indicating message IDs to be received;
A comparison unit that compares the transmission list report message with the reception list table and detects a message ID that is included in the reception list table but not included in the transmission list report message;
A message creating unit that creates the transmission request message related only to the message ID detected by the comparing unit;
The in-vehicle communication system according to claim 1, wherein the transmission request message created by the message creation unit is transmitted to the relay connection unit.   The in-vehicle communication system according to claim 1, wherein the bus connected to the electronic control unit and the relay connection unit includes a CAN communication line.   The in-vehicle device according to any one of claims 1 to 3, wherein transmission of a transmission list report message from the relay connection unit and transmission of a transmission request message from the electronic control unit are performed when a battery is connected. Communication system.   Transmission of the transmission list report message from the relay connection unit and transmission of the transmission request message from the electronic control unit are performed when the vehicle ignition key is operated to change from the off state to the accessory state or the on state. The in-vehicle communication system according to any one of claims 1 to 3.   In the basic routing table of the ROM of the relay connection unit, message IDs transmitted / received to / from the electronic control unit of the optional device that is not yet connected to the relay connection unit via the bus, The in-vehicle communication system according to any one of claims 1 to 5, wherein a correspondence relationship with the bus is also stored, and an additional routing table to be written to the RAM is reduced.   2. The transmission list report message transmitted from the relay connection unit is created by referring to both a basic routing table stored in the ROM and an additional routing table already written in the RAM. The in-vehicle communication system according to any one of claims 6 to 6.

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